Microalgae can be used to treat wastewater by harnessing their natural ability to efficiently consume nutrients – such as nitrogen and phosphate – from the surrounding environment. Optimising the growth of these algae is vital to the overall efficiency of the system; the more microalgae produced, the more nutrients can be removed, but it can be difficult to replicate the necessary environmental conditions to study this process in a lab setting. The team, based in England, could not rely on natural light alone for algal growth and, instead, tried using artificial lights and a flask on the benchtop, attempting to change the light profile simply by moving the flask nearer or further away from the lamps. This, however, did not help with controlling temperature, and a solution was needed that would be able to control both.

The discovery of Algenuity’s Algem photobioreactor allowed different operational parameters, including lighting and temperature, to be explored. Various environmental conditions could be replicated – set by simply entering geographical coordinates of wastewater treatment works all around the world – and the effects on the biomass yield were examined. Even the difference between conditions in June and December could be set at the click of a button, giving a true reflection of real-life conditions. Additionally, specific light wavelengths and photoperiods could be tested to see how they affect algal growth, with the potential of lowering the energy used from lighting through reduced light intensity and illumination periods.

To study these conditions, wastewater effluent was fed into the bioreactor where it was treated by the microalgae, and the purified water was collected. The wastewater was then tested to see how the algae were performing, and to keep a close eye on the best conditions for purification by tracking growth of the suspended algae using optical density.

The Algem bioreactors have completely changed the way the team works. The walkaway automation capabilities of the reactors allow complete experiments to be programmed in advance, for months at a time, improving time management, and having two flasks on each reactor enables each run to be done in duplicate, making it much quicker and easier to collect data. Overall, the Algem reactors have changed the institute’s approach to growth optimization, opening up many new options for experiments, and improving reproducibility. The next stage is to implement this research in an actual sewage treatment works to see if this microalgal approach can really make a difference on a large scale.